Mic fail on laptop (help)

[paul rope]

Well today I was going to use a mic on my laptop what is a Aspire7730, When I plug the mic in It cut off the speakers so I can't have sound at the same time.

Why is it doing this?

If you don't know where I am plugging mic into look at pic:

 

[paul rope]

I've had a look but I can't find any thing that is doing this.

 

[paul rope]

It's got a mic all ready built in it... But it's rely crap so that why I want to use a other 1.
Is they and way to do it so that it don't stop the sound?